Abstract
This paper presents a reliability-based approach for the analysis and design of a shallow strip footing subjected to a vertical load with or without pseudostatic seismic loading. Only the punching failure mode of the ultimate limit state is studied. The deterministic models are based on the upper-bound method of the limit analysis theory. The random variables used are the soil shear strength parameters and the horizontal seismic coefficient. The Hasofer-Lind reliability index and the failure probability are determined. A sensitivity analysis is also performed. The influence of the applied footing load on the reliability index and the corresponding design point is presented and discussed. It was shown that the negative correlation between the soil shear strength parameters highly increases the reliability of the foundation and that the failure probability is highly influenced by the coefficient of variation of the angle of internal friction of the soil and the horizontal seismic coefficient. For design, an iterative procedure is performed to determine the breadth of the footing for a target failure probability.
Highlights
In the analysis and design of geotechnical structures, all the input data have some degree of uncertainty and, may be considered as random variables or stochastic processes
A reliability-based analysis or design is more rational, since it takes into account the inherent uncertainty of each input variable
For both M1 and M2 failure mechanisms, the numerical results presented in this paper consider the case of a shallow strip foundation with breadth B = 2m
Summary
In the analysis and design of geotechnical structures, all the input data have some degree of uncertainty and, may be considered as random variables or stochastic processes. Traditional deterministic models simplify the problem by considering the uncertain parameters to be deterministic and by accounting for the uncertainties through the use of a global safety factor, which is essentially a “factor of ignorance.”. This factor is derived based on past experience and does not reflect the inherent uncertainty of each parameter. A reliability-based analysis or design is more rational, since it takes into account the inherent uncertainty of each input variable. Nowadays, this is possible because of the improvement of our knowledge on the statistical properties of the soilPhoon and Kulhawy 1999͒
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